The production of phenol and acetone by decomposition of cumene hydroperoxide is well known and has been in practiced commercially since the 1950's. Cumene hydroperoxide (CHP) itself is produced from the oxidation of cumene in a so-called oxidizer unit. The CHP thus produced is then concentrated in a distillation unit, typically to a concentration of 60% to 92% depending on the process. The concentrated CHP is then fed a decomposer (or cleavage) unit, where the acid decomposition of the CHP to phenol, acetone and other products such as alpha-methylstyrene occurs. In many cases, the concentrated CHP is diluted with cumene, acetone or water prior to being fed to the decomposer.
In some process designs it is desirable to accumulate a working volume of concentrated CHP from the distillation unit in an intermediate accumulation vessel and supply the decomposer unit from this working volume rather than directly from the distillation unit. In this design, the accumulated working volume is constantly turned over as concentrated CHP is fed from the accumulation vessel to the decomposer unit and fresh material is received by the accumulation vessel from the distillation unit.
The goal of accumulating a working volume to supply the decomposer is to provide a source of concentrated CHP to the decomposer unit in the event that an upset in the oxidizer and/or distillation unit temporarily interrupts the production of concentrated CHP. This is especially important in processes that conduct the decomposition of CHP in a boiling medium, where start-up or restart of the process after an upset is a hazardous operation. Even in non-boiling processes it can be of benefit to supply a working volume of concentrated CHP to avoid cavitation of pumps and transfer lines in the event of an interruption of the supply of CHP from the oxidizer and/or distillation unit.
Even though it is recognized as desirable to accumulate a working volume of concentrated CHP as described, this practice in itself presents special hazards. The decomposition of concentrated CHP is an extremely exothermic reaction, releasing approximately 1,421,000 joules/kg of heat for an 80 percent by weight solution. In some designs several thousand gallons of concentrated CHP may be accumulated. The potential for a catastrophic release of energy in the event of a mishap is therefore of great concern. A number of existing methods of accumulating working volumes of concentrated cumene hydroperoxide are not adequate to address this safety issue.
In a typical configuration for a process utilizing a boiling CHP decomposition unit, the accumulated volume of previously cooled CHP is simply stored in an unmodified tank or drum while only allowing a fraction of the accumulated volume to be used as a true working volume. In such designs the majority of the stored material exists as a stagnant volume with no circulation or mixed flow except for the natural in and out flow. Further such designs do not provide a means for direct cooling of the stored volume.
It would therefore be desirable to provide a method for storing a working volume of concentrated cumene hydroperoxide that alleviates the safety issues associated with storing extremely large volumes of stagnant concentrate without cooling.